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    <nav class="main">
        <a href="#terrestrial" class="open-popup">terrestrial animals</a>
        <a href="#aquatic" class="open-popup">aquatic animals</a>
    </nav>

    <section id="terrestrial" class="popup">
        <a href="#" class="back">&lt; back</a>
        <p>🦓🦒🐅🐆🐘🦏🐃🦌🐐🐫</p>
    </section>
    
    <section id="aquatic" class="popup">
        <a href="#" class="back">&lt; back</a>
        <p>🐋🐳🐬🐟🐠🐡🐙🦑🦐🦀</p>
    </section>
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